1. Field of the Invention
This invention relates to a display device which is capable of switching between a diffusing state and a transmitting state.
2. Description of the Related Art
Some of known display devices are arranged to provide a superimposed display by engraving pictographs or letters with micro-prisms on the surface of a viewfinder mat of the camera and illuminating them with a light emitting diode to impart the same color as the illuminating light to the pictographs or letters located within an area upon which the illuminating light is impinging. The display device of this kind is described, for example, in U.S. Pat. No. 5,053,803. FIG. 8 shows a viewfinder mat 101 arranged for a superimposed display according to the above-stated method.
Referring to FIG. 8, the viewfinder mat 101 is adapted for a single-lens reflex camera of the kind having five focus detecting points for automatic focusing. A focus detecting point where an object of shooting which is in focus is located among others is illuminated with the light of an external light-emitting diode to cause the focus detecting point to show up in a red color.
The prior art display device described above, however, has been found in need of some improvement in the following points
i) One light emitting source is required for every one of display parts which are arranged to provide a display independently of each other. Therefore, a total of five light emitting sources is required in a case where the camera has five focus detecting points like in the case of FIG. 8. These light emitting sources are arranged in the limited inside space of the camera complex and result in a cost increase.
ii) The display quality degrades, if the light of a display leaks to an adjacent display area to cause the adjacent display area to show up in part. To prevent this, the illuminating angle of the light emitting source must be severely adjusted and narrowed by using a lens.
iii) Generally, the viewfinder mat is made of a transparent moldable material such as an acrylic resin or the like. However, the use of such a material results in a poor transferability of the micro-prisms. Besides, the prism parts of molding dies are poor in durability.
iv) It is impossible to make the display color of one and the same display part variable from one color over to another, for example, to red, green or orange.